People are forgeting unmarked cars...
Here in the ACT, there isn't a model in the VZ series I haven't seen as a Police car. Even an unmarked Caprice and quite a few unmarked Calais'.
The SV6 is VERY popular with the ACT Traffic Ops guys as an un-marked car.
Here is my predicition:
Omega V6 - General Duties (marked and unmarked)
SV6 - Unmarked Traffic Duties / Unmarked Detectives / Seargent's (unmarked)
SS - Fully marked and high visibility cars for traffic ops and hwy patrol.
SSV, Berlina, Calais & CalaisV Unmarked - all duties (incl. dignantary [sp?] escort cars).
There won't be a VE the police won't have. Hell, they drive so many vehicles these days, Volkswagens, Mitsubish 380s, Volvos, Nissan X-Trails, Subarus, Mini Coopers, Ford Territorys, the whole Falcon line up, the list goes on!...